Introduction to the Cambridge White Spaces Trial

Cambridge-Trial-cover-2As wireless technology advances into ever smaller corners of our lives and businesses, the demands on electromagnetic spectrum grow rapidly. The challenge is that spectrum management evolves at a much slower pace.

In the early years, wireless communications was mostly voice and low data-rate traffic (telegraphy), requiring low bandwidth (narrow) channels. This allowed each application to be granted its own spectrum. As data traffic increases and high quality video becomes central to our communications this approach needs to change.

In the first place, although most spectrum has been allocated for one application or another, much of it lies idle for much of the time, in many places. [The UK regulator, Ofcom, and others have produced ample studies illustrating this untapped capacity. [Reference: Spectrum Framework Review, 2004]

In the second place, all applications are seeking ever higher bandwidth and hence wider spectrum channels, but there simply isn’t spare capacity available to support this, even if it were desirable.

Regulators have continued and tried to accelerate a ‘garbage collection’ approach to spectrum management, whereby old technologies are cleared out and the spectrum auctioned or otherwise assigned to new applications/communications technologies. However this process is slow and expensive and is in any case lagging far behind the rising demand for capacity. Instead, regulators need to develop mechanisms for sharing spectrum more intensively and effectively.

A brief history of television white spaces

cambridge 1The US regulator FCC was the first to explore this track in earnest, starting in the early 2000s, at the request of major ICT players who were keen to maximise Internet connectivity and saw wireless technology as a powerful enabler. These companies were aware of developments in cognitive radio technology which seemed to provide a powerful solution for the challenge of enabling licence exempt access in a licensed band, shared with major public services (i.e. television broadcasting) – and the original white space users (wireless microphones and other programme making/events gear).

Around 2006, Ofcom, which was contemplating a Digital Dividend (release of spectrum) from its digital television switchover programme.

Ofcom made a statement of commitment to opening TV white spaces subject to protecting existing services, in 2007. It then worked with industry to develop a framework which could deliver this. It also contributed to creating the necessary European regulation and standards to enable a Europe wide market for white space devices.

The road to the trial

Robyns-groupIn 2010, Ofcom reached the point where it felt it had either to halt its work on TVWS or invest seriously in preparing the novel and detailed regulation that would be required. To support the latter, it needed a strong indication of interest from the industry.

Industry responded by coming together in the Cambridge Trial, which Larkhill’s MD (Andrew Stirling), assembled and directed on behalf of Microsoft. There were 16 other leading companies involved in the trial from its inception in April 2011 to its conclusion in April 2012.

Results from the trial were highly influential, with UK policymakers and in regulatory discussions in Europe. It was a landmark on the road to dynamic spectrum access in Europe. There are still a few miles left on the journey, but Ofcom is now closing on the finishing line, with the enabling regulations expected to be in place by second half 2014.

You can study the trial reports for yourself:

  • The top-level findings and recommendations [Link]
  • A summary of the technical findings [Link]
  • More detailed reports on specific topics were produced by Adaptrum, Arqiva, BBC, CSR and TTP

The TVWS network in Cambridge is still in operation, supporting leading edge technology development, by Neul, in Cambridge.

Information on other trials and research being supported by Microsoft in this area can be found on this site.

Bute Trial

The Isle of Bute in Scotland also hosted a TV white spaces trial which was focussed on providing broadband to a rural community. It was supported by a Government grant (through the Technology Strategy Board) and the project’s participants included BT, BBC and the Centre for White Space Communications (CWSC). See http://www.wirelesswhitespace.org/ for more details about the trial findings and other research activities which are under way. The final report is here.

[Larkhill’s Managing Director is delighted to be the Chair of the Centre for White Space Communications.]

Around the world

Trials in Africa and Asia are now underway, tapping white space capacity to bring communities which have lacked even mains electricity into the increasing fraction of the world’s population which can now enjoy broadband Internet access, with the quality of life benefits that brings.